Water uptake by barley roots as affected by the osmotic and matric potential in the rhizosphere

Summary The water uptake rates of roots in saline soils are depressed by the simultaneously decreasing matric and osmotic water potentials in the soil surrounding the roots (rhizospheric soil). Unfortunately there are no reliable tools available for direct measurements of the effect of decreasing water potentials in the rhizospheric soil on the uptake rate of soil water by roots. This paper presents some results of a vegetation technique for studying the effect of different combinations of osmotic and matric water potentials in the rhizospheric soil on the water uptake rates of barley roots. Water uptake rates were reduced to a greater extent by decreasing soil matric water potentials than by decreasing soil osmotic water potentials. According to the results of this experiment, there was no relationship between the total soil water potential of a sandy soil and the water uptake rates when the roots were exposed to different combinations of and .     

Effects of root temperature on uptake of nitrate and ammonium ions by barley grown in flowing-solution culture

Summary Barley plants (Hordeum vulgare L.) grown from seed for 28 days in flowing solution culture were subjected to different root temperatures (3, 5, 7, 9, 11, 13, 17, 25°C) for 14 days with a common air temperature of 25/15°C (day/night). Uptake of NH₄ and NO₃ ions was monitored separately and continuously from solutions maintained at 10 M NH₄NO₃ and pH 6.0. Effects of root temperature on unit absorption rate , flux and inflow were compared. After 5 days , and increased with temperature over the range 3–11°C for NH₄ ions and over the range 3–13°C for NO₃ ions, with little change for either ion above these temperatures. Q₁₀ temperature coefficients for NH₄ ions (3–13°C) were 1.9, 1.7 and 1.6 for , and respectively, the corresponding values for NO₃ ions being 5.0, 4.5 and 4.6. For both ions, , and changed with time as did their temperature dependence over the range 3–25°C, suggesting that rates of ontogenetic development and the extent of adaptation to temperature may have varied among treatments.     

Are male rhesus monkeys more aggressive than females?

The justification for the “generalization that primate males are more aggressive than females” (Fedigan & Baxter, 1984) was tested in a troop of 24 captive rhesus monkeys. Males (N=9) were more dominant than females (N=15), i.e., they had more subordinate partners ( _m=17.0 vs. _f=6.6;p<0.01); hence, their aggression rate was higher ( _m=77.6 vs. _m=38.1;p<0.05). However, adjusting the rate of aggression according to the number of subordinate targets revealed no gender difference and males directed numbers of aggressive acts against individual subordinate partners that were not higher than those of females ( _m=4.4 vs. _f=5.4;p>0.1). It was concluded that aggressiveness is an individual attribute that is (1) independent of dominance status, and (2) independent of sex.     

The dissociation and separation of bovine adenohypophysial cells

Bovine adenohypophysial tissue was dissociated by sequential enzymatic incubation in a continuous flow system. Dispersed cells separated into discrete fractions after centrifugation in isopycnic bovine serum albumin gradients. The dispersed and separated cells were prepared for microscopic identification and differential counts by centrifugal cytology. Radioimmunoassays for LH, FSH, TSH, and Prl were used to corroborate the differential counts and determine the homogeneity of the fractions. The thyrotrophs banded at an average density ( ) of 1.0417, the FSH-secretory cells at , the LH-secretory cells at , and the Prl-secretory cells at . A 7–16 fold enrichment of different cell populations was possible. In bovine hypophyses each hormone appears to be formed by specific cells: the average TSH concentrations of the thyrotrophs were 5.1 pg/cell and the average LH and FSH concentrations were 4.7 and 4.9 pg/cell for LH-and FSH-secreting cells, respectively. The average Prl concentration was 4.9 pg/cell for Prl-secreting cells.     

Correlation between cell density,membrane fluidity,and the availability of transferrin receptors in friend erythroleukemic cells

Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity ( ), in accord with the culture cell density. At low cell density poise, whereas at confluency it increases to poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the erythropoiesis pathway.     

Use of the force-velocity test to determine the optimal braking force for a sprint exercise on a friction-loaded cycle ergometer

A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach the maximal velocity (V{immax}) against different braking forces (F _B). Power was averaged during a complete crank rotation by adding the power dissipated againstF _B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output ( ) power output attained atV _max ( ) calculated as the product ofV _max andF _B and the work performed to reachV _max expressed in mean power output ( ). The relationships between these parameters andF _B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken at rest to identify muscle metabolic and morphometric properties. The value was similar for allF _B. Therefore, the average of values was defined as corrected maximal power ( ). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the determination did not require high loads, the highest value ( ) was produced when loading was heavy, as evidenced by the -F _B parabolic relationship. For each subject, the braking force ( ) giving was defined as optimal. The , equal to 0.844 (SD 0.108) N · kg⁻¹ bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity ( ) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate kinase activity). Thus, from the determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer.     

Selenium deficiency in yugoslavia

Data on selenium (Se) deficiency in Yugoslavia are presented. The results include Se content of soil, cereal crops, and garlic grown in these soils, and human serum and scalp hair from several towns and regions. All data indicate a serious Se deficiency: soil (n=140), the mean value of 200±69.6 μg/kg Se; wheat, (58) = 20.5 ± 12.4 μg/kg; corn, (79) = 13.7 ± 13.6 μg/kg; and garlic, (66) = 13.7 ± 17.1 μg/kg Se. Analyses of human tissue show a very low Se status of the Yugoslav population: serum, (n=875) = 50.0 ± 18.0 μg/L and scalp hair, (388) = 94 ± 16 μg/kg Se. In some regions, Se contents of grain, garlic, and human serum and hair are approaching those in the low-Se belt in China. It is assumed that very low Se status of a human population could be a risk factor in the development of Balkan Endemic Nephropathy (BEN) and in a high incidence of urinary tract tumors (UTT) in endemic areas. A portion of these results were presented at the International Symposium on Selenium, Belgrade, May 12–15, 1991, Abstracts p.1, Serbian Academy of Sciences and Arts.     

The applicability of the rooting technique measuring salt resistance in populations ofFestuca rubra andJuncus species

Summary Indices of salt resistance, based on the measurement of the Mean Relative Growth Rate of the total plant biomass were shown to be more reliable and easily obtained than those based on the rooting technique. Adaptation to salinity stress (NaCl toxicity, osmotic stress) differs essentially from heavy metal stress (mainly ion-toxicity). Extension of the root system under saline conditions should therefore be regarded as a compensatory growth mechanism rather than the direct result of salt stimulation. The application of the rooting technique for optimum measurement of salt resistance is questioned. The index of salt resistance technique may be applied to all vascular plants, while unmodified application of the rooting technique is confined to certain groups of the Monocotyledonae.     

The\dot V_A /\dot Q resolution of inert gas dataresolution of inert gas data

The non-uniqueness of distributions satisfying inert gas retention data without error is studied. The ability of such data to resolve blood flows at particular values is discussed through the application of linear programming and Backus-Gilbert theory. It is shown that the resolution deteriorates away from the extremes of low and high .     

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle

Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth ( ) increased with the addition of Ca²⁺ or with the depletion of ATP. The increase in the with the addition of Ca²⁺ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca²⁺. The increase in which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in following the addition of Ca²⁺ was found to be seasonal, i.e., values of obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca²⁺ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS dynamic light scattering - L length - K scattering vector - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - average characteristic line width Deceased     

Influence of lifting technique on perceptual and cardiovascular responses to submaximal repetitive lifting

Oxygen consumption ( O₂), heart rate, ventilation and central rating of perceived exertion (RPE) in repetitive lifting while executing squat and stoop techniques were investigated in ten male forestry workers. In all five mass/frequency combinations studied, O₂ was significantly higher for the squat than for the stoop technique. No differences were found in RPE between the techniques. The O₂ and RPE recordings were also related to those obtained during maximal repetitive lifting (same lifting technique) and maximal treadmill running. The O₂ expressed as a percentage of that obtained during maximal repetitive lifting with the same lifting technique was defined as relative aerobic intensity (% O_{2max, lifting}). The % O_{2max, lifting} was not significantly different between the techniques except for the lowest mass lifted (1 kg). This study therefore would support the hypothesis that RPE is more closely related to % O_{2max, lifting} than to absolute aerobic intensity. Related to maximal treadmill running, it was demonstrated for both lifting techniques that relative RPE (percentage of the RPE during maximal running) was more accurate than relative O₂ (percentage of maximal O₂ during maximal running) for determining the % O_{2max, lifting} in repetitive lifting. The study showed that the higher O₂ during squat. lifting compared to stoop lifting was caused by the O₂ expended in lifting and lowering the body rather than the O₂ expended lifting and lowering the external mass. It was concluded that the stoop technique was not superior to the squat technique in terms of central RPE. Based on % O_{2max, lifting}, there may be a rationale for choosing the stoop technique during repetitive lifting with light masses, but not with heavy masses.     

Aerobic and anaerobic contribution to Wingate test performance in sprint and middle-distance runners

We investigated the aerobic and anaerobic contributions to performance during the Wingate test in sprint and middle-distance runners and whether they were related to the peak aerobic and anaerobic performances determined by two commonly used tests: the force-velocity test and an incremental aerobic exercise test. A group of 14 male competitive runners participated: 7 sprinters, aged 20.7 (SEM 1.3) years, competing in 50, 100 and 200-m events and 7 middle-distance runners, aged 20.0 (SEM 1.0) years, competing in 800, 1,000 and 1,500 m-events. The oxygen uptake ( ) was recorded breath-by-breath during the test (30 s) and during the first 20 s of recovery. Blood samples for venous plasma lactate concentrations were drawn at rest before the start of the test and during the 20-min recovery period. During the Wingate test mean power ( ) was determined and three values of mechanical efficiency, one individual and two arbitrary, 16% and 25%, were used to calculate the contributions of work by aerobic ( _{aer,ind,16%,25%}) and anaerobic ( _{an,ind,16%,25%}) processes. Peak anaerobic power ( _an,peak) was estimated by the force-velocity test and maximal aerobic energy expenditure ( _aer,peak) was determined during an incremental aerobic exercise test. During the Wingate test, the middle-distance runners had a significantly greater than the sprinters (P < 0.001), who had significantly greater venous plasma lactate concentrations (P < 0.001). Moreover, _{aer,ind,16%,25%} were also significantly higher (P < 0.05) in the middle-distance runners [ _aer,ind 45 (SEM 4) % vs 28 (SEM 2) %; _aer,16% 30 (SEM 3) % vs 19 (SEM 2) %; _aer,25% 46 (SEM 3) % vs 29 (SEM 2)%]; _{an,ind,16%,25%} in the sprint runners (P < 0.05) [ _an,ind 72 (SEM 3) % vs 55 (SEM 4) %; _an,16% 81 (SEM 2) % vs 70 (SEM 3) %; _an,25% 71 (SEM 2) % vs 54 (SEM 3) %]. The _aer,ind/ _aer,peak and × _an,ind/ _an,peak ratios, however, were not significantly different between the two groups of athletes. These results would indicate that the sprinters and middle-distance runners used preferentially a metabolic system according to their speciality. Nevertheless, under the conditions of its experiment, they seemed to rely on the same percentage of both peak anaerobic and peak aerobic performance for a given exercise task.     

Analysis of spatial association between two species based on the interspecies mean crowding

Summary and Conclusion The measurement of spatial association between two species is considered on the basis of interspecies mean crowding. Two indices of overlapping, γ andC _μ, are derived as geometric and weighted arithmetic means of the same component ratios related to inter- and intraspecies mean crowdings. Both indices behave in a similar way, ranging from 1 when the distributions of two species are completely overlapped to 0 when they are completely exclusive with each other. The former is essentially identical with indices proposed byKuno (1968) andPianka (1973), and the latter is a modified form ofMorisita’s (1959)C _δ index. Indices to measure the degree of spatial correlation between species, ω andR _μ, are then derived for both kinds of overlapping indices, which vary from 1 in complete overlapping, through 0 in independent occurrence, to −1 in complete exclusion. Various kinds of interspecies association are analyzed using these indices and an extended form of the regression graph which provides a convenient way of indicating the spatial interrelation between two species as well as distribution patterns of respective species. The method presented in this paper may also be applicable to compare temporal distribution patterns between species, similarity between communities, etc. For such a wider application which includes continuous as well as discrete distributions, the interpretation of intra- and interspecies mean crowdings is not necessarily appropriate, and hence the concept of mean concentration with the symbols and for intraspecies relation and and for interspecies relation is suggested. This study was supported by Science Research Fund (No. 148041) from the Ministry of Education.     

The height and weight of Kuwaiti pre-school children

This paper consider the effect of age-grouping on the distribution of two variables, namely, height and weight of pre-school children subject to growth. Assuming straight line regression models for the dependence of expected values as well as variances and covariance of height and weight was investigated by Ehrenberg's law-like model. Ehrenberg's law-like relationship between height and weight, Log , was applied to Kuwaiti children under 7 years of age. It was found that the relationship log was a good fit for Kuwaiti boys and girls except for children under 1 year where the results were significantly different from the expected value     

Cardiovascular responses to sustained maximal isometric contractions of the finger flexors

This study investigated cardiovascular responses to 2 min sustained submaximal (20% MVC) and maximal (100% MVC) voluntary isometric contractions of the finger flexors in healthy young women. Cardiovascular variables investigated were: heart rate (f _c), mean arterial pressure ( _a), and stroke volume (SV). Doppler echocardiography was used to estimate SV from measures of aortic diameter (AD) and time-velocity integrals. Preliminary studies indicated that AD did not change significantly after 2 min sustained 100% MVC. Therefore, pre-exercise AD values were used to calculate SV before, during and after exercise. During the 2-min 100% MVC period, f _c and _aincreased significantly during the first 30 s of contraction. f _c then remained constant during the remainder of the 2-min contraction period, while _acontinued to rise. SV did not change significantly during the 100% MVC task but increased significantly during recovery from sustained 100% MVC. The data suggest that the magnitude of cardiovascular responses to isometric exercise is dependent on the specific task performed, and that there is a different pattern of response for f _c, _a, and SV during 20% and 100% MVC tasks. Unlike f _c and _a, SV did not change significantly during isometric exercise, but increased significantly after sustained 100% MVC.     

Phytoplankton dynamics,primary productivity and community metabolism in a north-central Texas pond

Phytoplankton diversity, primary productivity and community metabolism were measured for 1 year in a 0.94 ha pond located in north-central Texas. Gross primary production ranged from 4.5 to 46.8 kcal m⁻² day⁻¹ ( =22.0 kcal m⁻² day⁻¹) and community metabolism ranged from 7.3 to 32.4 kcal m⁻² day⁻¹ ( =14.8 kcal m⁻² day⁻¹). Average production/respiration ratio (1.5) showed that the pond was principally autotrophic. Photosynthetic efficiency (gross primary production/0.5 total solar radiation) ranged from 0.32 to 2.8 with a mean of 1.2. Phytoplankton diversity based on numbers and biomass fluctuated greatly. Highest gross primary productivity occurred during Cyanophyta blooms in late summer-early fall when species diversity was minimal. Water temperature and turbidity, which governed light penetration, were the principal determinants of primary production.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

The nucleotide sequence ofBeneckea harveyi 5S rRNA

Summary The complete sequence of the 5S rRNA from the bioluminescent bacterium,Beneckea harveyi has been determined to be p U G C U U G G C G C C A U A G C G A U U-G G A C C C A C U G A (U) C U U C A U U C C-G A A C C A G A A G U G A A C G A A U U A-G G C C G A U G G U G U G U G G G G C U-C C C C A U G U A G A G U A G G A A U C G-C C A G G U (U)_OH.Two sites of sensitivity to ribonuclease T₂ cleavage were identified; at A₄₁ and either A₅₄ or A₅₅. Comparison with existing sequence information fromEscherichia coli andPhotobacterium phosphoreum clarifies the amount of diversity among the bioluminescent bacteria and provides further insight into their phylogenetic position. Sequence heterogeneities were encountered and the importance of these in interpreting 5S rRNA data is discussed.     

Reciprocal inhibition of human motoneurons with different firing frequencies

A study was made of the effect of reciprocal inhibition on individual firing motoneurons in the extensor carpi ulnaris and soleus muscle in human subjects. Peristimulus histograms (PSH) were plotted at different average frequency of motoneuron firing ( ) and the change in duration of interspike intervals (ISI) was analyzed. For reciprocal inhibition, as for other types of inhibition, is a factor in the effectiveness of motoneuron inhibition. The duration of inhibition apparent in the PSH, the sizes of zones of inhibition effectiveness in the ISIs and lengthening of the intervals are dependent on . For all motoneurons, the low range is most favorable for effective inhibition. The dependence of effectiveness of a volley on the time of its arrival within the ISI is also analyzed.Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 24, No. 6, pp. 643–653, November–December, 1992.     

Breathing pattern and growth: comparative aspects

Summary The resting oxygen consumption and breathing pattern of nine newborn and adult species (ranging in body size from mouse to human) have been compared on the basis of data collected from the literature. Minute ventilation is similarly linked to at both ages, the percent of extracted as O₂ about 2.2. Tidal volume/kg is an interspecies constant in newborns and adults, approximately 8 ml/kg. Breathing frequency decreases with the increase in size in a different way at the two ages: large species have newborns breathing at rates 2–3 times above the corresponding adults' values, while in the small species newborns and adults breathe at almost the same rate. Therefore the newborns of the smallest species have both and below the expected values, implying a greater inability to cope with the external demands than newborns of larger species. Several considerations indicate that in the smallest newborns the mechanical properties of the respiratory system could be a constraint to resting ventilations larger than observed. It is therefore possible that their low is the cause, and not the effect, of the relatively small .